The Efficacy of Commercial Surface Sanitizers against Norovirus on Formica Surfaces with and without Inclusion of a Wiping Step

ABSTRACT Commonly used surface sanitizers often lack activity against human noroviruses (hNoVs). The impact of inactivation versus removal when these products are applied via wiping is poorly characterized. The purpose of this work was to assess the anti-hNoV efficacy of various surface sanitizer chemistries, as applied to a laminate material commonly used for restaurant tabletops, using standard surface assays (ASTM E1053-11) and a newly developed wiping protocol. Four commercially available products with different active ingredient(s) (i.e., ethanol [EtOH], acid + anionic surfactant [AAS], quaternary ammonium compound [QAC], and sodium hypochlorite [NaOCl]) and a water control were evaluated against hNoV GII.4 Sydney, hNoV GI.6, and the cultivable surrogate Tulane virus (TuV). Virus concentration was evaluated using RNase-reverse transcriptase (RT)-quantitative PCR (qPCR) (hNoV) and infectivity assay (TuV). Only the EtOH-based product significantly reduced virus concentration (>3.5 log10 reduction [LR]) by surface assay, with all other products producing ≤0.5 LR. The inclusion of a wiping step enhanced the efficacy of all products, producing complete virus elimination for the EtOH-based product and 1.6 to 3.8 LR for the other chemistries. For hNoVs, no detectable residual virus could be recovered from paper towels used to wipe the EtOH-based product, while high concentrations of virus could be recovered from the used paper towel and the wiped coupon (1.5 to 2.5 log10 lower genome equivalent copies [GEC] compared to control) for the QAC- and AAS-based products and for water. These results illustrate the variability in anti-hNoV activity of representative surface sanitizers and highlights the value of wiping, the efficacy of which appears to be driven by a combination of virus inactivation and removal. IMPORTANCE Human noroviruses (hNoVs) are the leading cause of acute gastroenteritis and food-borne disease worldwide. Noroviruses are difficult to inactivate, being recalcitrant to sanitizers and disinfectants commonly used by the retail food sector. This comparative study demonstrates the variability in anti-hNoV activity of representative surface sanitizers, even those allowed to make label claims based on the cultivable surrogate, feline calicivirus (FCV). It also highlights the importance of wiping in the process of sanitization, which significantly improves product efficacy through the action of physical removal of surface microbes. There is a need for more and better product formulations with demonstrated efficacy against hNoVs, which will likely necessitate the use of alternative cultivable surrogates, such as Tulane virus (TuV). These findings help food safety professionals make informed decisions on sanitizing product selection and application methods in order to reduce the risk of hNoV contamination and transmission in their facilities.

Rnf stoichometry is dependent on chemiosmotic potential well as substrate and product mid point potential. I have used the book Bioenergetics 4 (2013)

by David Nicholls and Stuart Ferguson as my main reference for all equations
Rnf has only been characterized biochemically as a Na pump in acetogens, The authors determined a stoichiometry of 2 Na + / electrons from reduced ferredoxin (Fd) to NADH. While Rnf has not been characterized in aerobic metabolism where it most likely uses the consumption of protons to facilitate the reduction of Fd from NADH. By determining the stoichiometry we can see how Rnf interacts with the whole electron transport system. (Below) To determine the effect of the ratio has on the thermodynamics of Rnf we will calculate the mid-point potential of using the Nerst equation: Where is the gas constant, is the Faraday constant To utilize the Nerst equation we will use the ratio from Figure 2B: Where is the ratio.
We can use python to calculate the above equation and calculate the cellular redox potential for any ratio of : So we can see that while the does effect the mid point potential only in the extremes is it going to cause some reactions to be infeasible or something like NADH reducing ferredoxin or flavodoxin which have a mid point potential around -500 mv.
These answers from above now allow us to ask what the of the Rnf reaction.
First lets lay out the stoichiometry of the reaction: Where is periplasm proton and is the cytoplasm proton and is the number of protons translocated.
For the redox reaction between NADH and Fd we must calculate : Where the midpoint potential of Flavodoxin is -483 mv (Segal et al 2016), so is: Then to calculate we use: Giving: The is positive as Fd is at a lower mid point potential than NADH hence the need for proton motive force to drive this reaction forward.
The proton motive force was measured once in A. vinelandii in Laane et al (1980) and present as the electric potential at and the change in pH at . We can calculate the proton motive force in for or for through the following equations: With this information we now have two ways of calculating the protons required to facilitate electron transfer. First when electrons enter and leave the on the same side of the membrane we can use the simple relationship between proton motive force and the redox span: Where is the proton motive force in mv and is the number of protons required for translocation and the 2 for the 2 electrons transfer in the redox span. Solving for gives: The next way to calculate using the and by understanding that in order to make the reaction favorable Meaning the of the redox reaction must at least equal the or Both of ways are very similar and probably only different due rounding errors. We can round the stoichiometry to This is similar to the stoichiometery given for proton pumping with acetogens and which is annotated in most databases for RNF.

Rnf and the relationship to proton motive force
Now we can take this information and show how Rnf would be influenced by the proton motive force and how this could make it a conditionally enzyme with use under higher proton motive forces.
We can simply plot the relationship between the of Rnf and and plot the linear relationship: To convert to mV we will use To graph below we will use